• 대한화학회지
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• 제60권3호
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• pp.169-176
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• 2016

Borate 완충용액에서 Al의 부식과 부동화에 관하여 변전위법, 대 시간 전류법 그리고 다중 주파수 전기화학적 임피던스 측정법으로 조사하였다. 공기 또는 산소의 영향은 환원과정에 영향을 주었지만 산화반응에는 영향을 미치지 못 하는 것으로 보인다. 부동화 영역에서 생성되는 피막의 전기적 성질은 Mott-Schottky 식이 적용되는 n-type 반도체 성질을 보였다. 낮은 전극전위에서 생성되는 Al의 산화피막은 Al(OH)₃로 충분한 부동화 효과를 보이지 못하나, 전극전위가 증가하면서 Al₂O₃로 변하였다. Al₂O₃ 피막은 “전기장에 의한-이온의 이동” 과정에 의하여 성장하는 것으로 보인다.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.3052-3058
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• 2014

In this article, we have designed and synthesized a novel donor-${\pi}$-acceptor (D-${\pi}$-A) type porphyrin-based sensitizer (denoted UI-5), in which a carboxyl anchoring group and a 9,9-dimethyl fluorene were introduced at the meso-positions of porphyrin ring via phenylethynyl and ethynyl bridging units, respectively. Long alkoxy chains in ortho-positions of the phenyls were supposed to reduce the degree of dye aggregation, which tends to affect electron injection yield in a photovoltaic cell. The cyclic voltammetry was employed to determine the band gap of UI-5 to be 1.41 eV based on the HOMO and LUMO energy levels, which were estimated by the onset oxidation and reduction potentials. The incident monochromatic photon-to-current conversion efficiency of the UI-5 DSSC assembled with double-layer (20 nm-sized $TiO_2$/400 nm-sized $TiO_2$) film electrodes appeared lower upon overall ranges of the excitation wavelengths, but exhibited a higher value over the NIR ranges (${\lambda}$ = 650-700 nm) compared to the common reference sensitizer N719. The UI-5-sensitized cell yielded a relatively poor device performance with an overall conversion efficiency of 0.74% with a short circuit photocurrent density of $3.05mA/cm^2$, an open circuit voltage of 0.54 mV and a fill factor of 0.44 under the standard global air mass (AM 1.5) solar conditions. However, our report about the synthesis and the photovoltaic characteristics of a porphyrin-based sensitizer in a D-${\pi}$-A structure demonstrated a significant complex relationship between the sensitizer structure and the cell performance.

• 대한화학회지
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• 제43권3호
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• pp.264-270
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• 1999

Immobilon-AV 친화성 막에 glucose oxidase[EC1.1.3.4](725units/mL)를 고정하여 백금 전극에 부착시킨 전극을 사용하여 glucose를 전류법으로 정량하였다. 이때 glucose가 gluconic acid로 산화될 때 전류를 +0.8V vs. Ag/AgC1에서 측정하였다. 효소 고정화된 막을 부착시킨 전극의 감응 특성은 다음과 같다. 직선 감응범위는 0.2mM에서 20mM이었으며, 정량한계는 10-3 mM이었다. 또한 감응 시간은 12초, 효소 고정화된 막의 최적 pH(CH3COONa/CH3COOH)는 5.5, 그리고 수명은 27일 이였다. 그리고 다른 생리 활성물질의 방해는 없었다. 또한 고구마를 이용하여 AOAC 방법으로 정량한 glucose 측정값을 비교해 본 결과, 그 상대오차는 0.1%였다.

• Corrosion Science and Technology
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• 제8권4호
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• pp.143-147
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• 2009

In biomedical implants and dental fields, titanium has been widely utilized for excellent corrosion resistance and biocompatibility. However, Ti and its alloys are nonbioactive after being implanted in bone. In this study, for the purpose of improvement in biocompatibility the anodic $TiO_2$ layer on Ti-xNb alloys were fabricated by electrochemical method in phosphate solution, and the effect of Nb content on the pore size, the morphology and crystallinity of Ti oxide layer formed by the anodic oxidation method was investigated. The Ti containing Nb up to 3 wt%, 20 wt% and 40 wt% were melted by using a vacuum furnace. The sample were cut, polished, and homogenized for 24 hr at $1050^{\circ}C$ for surface roughness test and anodizing. Titanium anodic layer was formed on the specimen surface in an electrolytic solution of 1 M phosphoric acid at constant current densities ($30mA/cm^2$) by anodizing method. Microstructural morphology, crystallinity, composition, and surface roughness of oxide layer were observed by FE-SEM, XRD, EDS, and roughness tester, respectively. The structure of alloy was changed from $\alpha$-phase to $\beta$-phase with increase of Nb content. From XRD results, the structure of $TiO_2$ formed on the Ti-xNb surface was anatase, and no peaks of $Nb_2O_5$ or other Nb oxide were detected suggesting that Nb atoms are dispersed in $TiO_2$-based solid solution. Surface roughness test and SEM results, pore size formed on surface and surface roughness decreased as Nb content increased. From the line analysis results, intensity of Ti peak was high in the center of pore, whereas, intensity of O peak was high in the outside of pore center.

• 대한화학회지
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• 제18권5호
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• pp.373-380
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• 1974

저자들에 의해서 이미 보고되어 있는 요오드화염으로부터 요오드산염$(I^-{\to}{IO_3}^-)$ 및 요오드산염으로 부터 과요오드산염$({IO_3}^-{\to}{IO_4}^-)$까지의 전해결과를 참작하여 무격막 전해조와 이산화납양극을 사용하여 요오드화염으로부터 과요오드산염$(I^-{\to}{IO_4}^-)$을 직접 전해제조하기 위한 최적 전해조건에 관하여 검토하였다. 0.5g/l의 환원방지제인 중크롬산칼륨을 함유함 1몰의 요오드화칼륨 수용액을 15A/$dm^2$의 양극전류밀도와 $60^{\circ}C$의 전해온도에서 전해한 결과, 요오드화칼륨으로 부터 과요오드산칼륨까지의 변화율 98%에서 전류효율이 84%이었다. 또한 각종 전해액중에서 이산화납 양극에 의한 분극곡선으로 부터 전극반응의 내용도 설명하였다.

• Korean Chemical Engineering Research
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• 제46권4호
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• pp.686-691
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• 2008

산화아연은 광학적/전기적 특성 때문에 많이 연구되고 있는 재료이지만 산, 염기분위기에 약하기 때문에 양극 산화법을 이용하여 제조하기 힘들며, 현재 보고 되어 지고 있는 연구결과 역시도 많지 않다. 본 논문에서는 일반적인 전해질인 수용액이 아닌 에탄올과 $H_2SO_4$의 혼합용액을 사용하여 양극산화 하였으며 수용액에서 제조된 ZnO와는 다른 자기 정렬된 줄무늬의 육각판상구조를 가진 ZnO를 제조할 수 있었다. 이는 $H_2SO_4$를 함유한 에탄올용액에서 $H_2SO_4$에 미량 포함된 $H_2O$가 ZnO의 선택적인 용해를 함으로서 자기 정렬된 구조를 만드는데 기인한다. $H_2SO_4$의 농도, 인가전압, 양극산화 시간, 물 첨가 등에 따른 영향 및 자기 정렬된 줄무늬의 육각판상구조를 생성하는 메커니즘을 다루었다.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.167-173
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• 2013

A series of highly efficient red phosphorescent heteroleptic iridium(III) complexes 1-6 containing two cyclometalating 2-(2,4-substitued phenyl)quinoxaline ligands and one chromophoric ancillary ligand were synthesized: (pqx)$_2Ir$(mprz) (1), (dmpqx)$_2Ir$(mprz) (2), (dfpqx)$_2Ir$(mprz) (3), (pqx)$_2Ir$(prz) (4), (dmpqx)$_2Ir$(prz) (5), (dfpqx)$_2Ir$(prz) (6), where pqx = 2-phenylquinoxaline, dfpqx = 2-(2,4-diflourophenyl)quinoxaline, dmpqx = 2-(2,4-dimethoxyphenyl)quinoxaline, prz = 2-pyrazinecarboxylate and mprz = 5-methyl-2-pyrazinecarboxylate. The absorption, emission, electrochemical and thermal properties of the complexes were evaluated for potential applications to organic light-emitting diodes (OLEDs). The structure of complex 2 was also determined by single-crystal X-ray diffraction analysis. Complex 2 exhibited distorted octahedral geometry around the iridium metal ion, for which 2-(2,4-dimethoxyphenyl)quinoxaline N atoms and C atoms of orthometalated phenyl groups are located at the mutual trans and cis-positions, respectively. The emission spectra of the complexes are governed largely by the nature of the cyclometalating ligand, and the phosphorescent peak wavelengths can be tuned from 588 to 630 nm with high quantum efficiencies of 0.64 to 0.86. Cyclic voltammetry revealed irreversible metal-centered oxidation with potentials in the range of 1.16 to 1.89 V as well as two quasi-reversible reduction waves with potentials ranging from -0.94 to -1.54 V due to the sequential addition of two electrons to the more electron-accepting heterocyclic portion of two distinctive cyclometalated C^N ligands.

• 대한화학회지
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• 제28권5호
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• pp.271-278
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• 1984

염기성 용액에서 기계적으로 연마한 고순도 철의 전위를 환원 전위로부터 부동화 전위로 급격히 변화시켜서 부동화 막이 전극표면에 형성되게 하면서 철의 반사율 변화와 타원편광반사법(Ellipsometry) 측정을 하였다. 철 표면이 부동화 될때 일어나는 반사광의 편광 파라메터(${\Delta},\;{\psi}$)와 반사율(R) 변화를 자동화된 타원편광반사계로 기록하였고, 이로부터 철을 부동화 상태에 들어가게 하는 표면막의 두께(${\tau}$)와 광학상수(n, k)들의 변화하는 값을 계산할 수 있었다. 광학상수 값들로 나타나는 막의 성질이 시간에 따라 급격한 전이를 하는 것은 관찰되지 않았으며, 비교적 짧은 시간(수초)내에 정상 상태 값에 접근하였다. 효과적으로 부동화를 일으키는 막의 두께는 $14\;{\sim}\;23{\AA}$의 범위에 있었다. 형성된 부동화 막은 용액의 pH가 큰 경우에는 얇고 치밀한 구조를 가진 것으로 보이며, pH가 작은 경우에는 두께는 두껍지만 pH가 큰 경우보다 덜 치밀한 부동화 막이 형성되는 것으로 보였다. 이들 부동화 막은 약간의 흡광성을 가지는 것으로 나타났다.

• 한국수소및신에너지학회논문집
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• 제3권2호
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• pp.25-33
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• 1992

With the aim to obtain $TiO_2$ films with an increased photorespones and absorbance in the visible region of the solar spectrum, the direct oxidation of titanium alloys were performed. In this study, $Ti-Ga_2O_3$ alloy was prepared by mixing, pressing and arc melting of appropriate amounts of titanium and $Ga_2O_3$ powder. Electrochemical measurements were performed in three electrode cell using electrolyte of 1M NaOH solution. The oxide films on $Ti-Ga_2O_3$ alloy was composed of $Ti_2O$, TiO, $TiO_2$, $Ga_2TiO_5$. The free energy efficiency (${\eta}e$) of $Ti-Ga_2O_3$ oxide films had 0.8~1.3 % and were increased with the increase of $Ga_2O_3$ content up to 10wt %. The onset potential ($V_{on}$) had -0.8V~0.9V ranges and were shifted to anodic direction with the increase of $Ga_2O_3$ content. The spectral response of Ti-$Ga_2O_3$ oxides were similar to the response of the $TiO_2$ and their $E_g$ were observed to 2.90~3.0eV. Variations of onset potential($V_{on}$) associated with electrolyte pH were -59mV/pH. This probably reflects the nature of the bonding of $OH^-$ ion to the $TiO_2$ surface, a common phenomena in the transition-metal oxides.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2004년도 수소연료전지공동심포지움 2004논문집
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• pp.103-108
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• 2004

The present paper relates to an apparatus in which all carbonaceous material such as coal, oil, plastics and any substance having carbon atoms as part of its constituents are reformed(gasified) into syngas at temperature above $1,200^{\circ}C$(KR patent No.0391121, and PCT/KR2001/01717 and PCT/KR2004/001020). It comprises a single-stage reforming reactor without catalyst and a syngas burner as shown in Fig.2. syngas is combusted with $O_2$ gas in the syngas bunter to produce $M_2O$ and $CO_2$ gas with exothermic heat. Reaction products are introduced into the reforming reactor, reaction heat from syngas burner elevate the temperature of reactor above $1,200^{\circ}C$, and reaction products reduce carbonaceous material down to CO and $H_2$ gases. Reactants and heat necessary for the reaction are provided through the syngas burner only, Neither $O_2$ gas nor steam are injected into the reforming reactor. Reformer is made of ceramic inner lining and sst outer casing. Multiple syngas burners may be connected to the reforming reactor in order to increase the syngas output, and a portion of the product syngas is recycled into syngas burner. The present reformer as shown in Fig.2 is suitable to gasify carbonaceous wastes without secondary pollutants formed from oxidation. Further, it can be miniaturized to accompany a fuel cell system as shown in Fig.3 The output syngas may be used to drive a fuel cell and a portion of electrical power generated in a fuel cell is used to heat a compact reformer up to $1,200^{\circ}C$ so that gas/liquid fossil fuel can efficiently reformed into syngas. The fuel cell serves as syngas burner in Fig.2. The reformation reaction is sustained through recycling a portion of product syngas into a fuel cell and using a portion of electric power generated to heat the reformer for continuous operation. Such reforming reactor may be miniaturized into a size of PC, then you have a Personal Reformer(PR).